i love the idea of oval chainrings but feel like there are so many grey areas.

isnt' actually the optimum position different from what you describe?

Quoting from noncircularchainring.be

You may be right...I'll have to look at that...I've found it confusing that in their diagrams they are looking at the chainring from the NDS :-/

Looks like I'm going to have to retest some stuff if that's the case. Doh!

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http://bikeblather.blogspot.com/

Question,

if you rotated the rings 90 degrees, say in the "wrong" position like the old bio-pace do you think you would see a "negative" inflation factor on the quarks.

(like a 56 gear at TDC and BDC, and a 51 gear at 90 degrees)

I guess it depends on foot speed through out the pedal stroke and if its affected the same but at opposite points.

Might not be the best idea for the knees, just curious as I was looking at a quark but may make other choices.

Yes, logically that would result in the power being under-reported since the average rotational velocity would be actually lower than the rotational velocity occuring during the highest torque output of the pedal cycle.


Hmmm...if it was a choice between non-round rings and a Quarq, I think I have a feeling which way I'd lean... ;-)

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http://bikeblather.blogspot.com/

this should be the "optimal" orientation based on their mathematical model, it'd make sense because it accounts 1)the fact that vastus lateralis is more activated compared to the default, "max inertia" position + maximal hamstring activation, which is the higher end torque phase and 2) it's the phase of maximal rate/increase of torque and not just the resulting maximal final (with a cranck at ~108°-110° or ~18-20° under horizontal crank compared to ground).

Correct but with a rotor even a rotor xl you will probably see little to no power delta.

right, it's just an example
as it's also what I've now (togheter with Ogival and Stronglight installed on another bike) while waiting for Doval and O'symetric to arrive, it's quite a long way from SK and USA to Italy :)

According to this interview/piece...'I asked an SRM engineer about the possibility of this and he tells me that it would be impossible for the osymetric chainrings to affect the readings of an SRM powermeter.'

http://www.cyclingtips.com.au/...-gimmick-or-miracle/

Thought it was a good article. Found the bit about Wiggins and co switching to round rings to train on a week before a race to get a 'turbo boost' then switching back the day before the start interesting.

Yeah...I've seen that comment. I hate to say it, but the author of that article either talked to the wrong engineer at SRM, or the engineer doesn't understand the issue...or both.

This was all "sussed out" way back in 2006 on the Wattage list in a thread started by Jens Heycke were he reported observing a difference in SRM vs. PT reported power when using round rings, Rotor rings, and Osymetrics when riding outside:

https://groups.google.com/...rBUKY20s0/discussion

Ironically, even back then, the SRM "expert" on the thread (Jason Yanota) didn't seem to quite grasp the issue...


Meh...


Placebo is a powerful thing!

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http://bikeblather.blogspot.com/

Tom,

I'm sure this was answered somewhere so sorry for asking, but do you consider a Powertap an accurate tool to measure any potentiel improvement (if there is one) with non round chainrings as opposed to round.

I've just ordered a new Powercranks (let's not start the powercranks debate... please guys) with the Dual mode (which I don't normally use), I'm considering testing different things with it :
- install two 50T rings, one round and then one Qring which I might change for an Osymetric after that, look at power / heart rate / feel of exhaustion.
- change crank lenght with 5mm steps, starting at 165mm (my actual crank lenght on TT bike) and then removing 5mm and increase saddle height 5mm (don't think I'll actually change bar height for the test) and so on. I can probably do thing also with the two different rings on.

I have a Powertap G3 on the back of my 596 with Powercranks so there is probably a chance I can test both separately but also at the same time, I read your suggestion that shortening the crank arms might actually provide a similar feeling/"benefit" (again if any) as riding the Osymetric ring.

I'm happy to discuss that with you and maybe the testing I can do can complement what you are doing on your side. But first I need to make sure the Powertap can provide accurate results, because differences we are trying to measure are so small that if the non round ring tend to provide non-accurate results even on Powertap then there is no point in trying to measure anything (I'll still work on the crank lenght thing though as it is what I'm most interested in right now).

Thanks Tom for any help you can provide.

Yes. The PT uses a different calculation algorithm (time based vs. "event" based) and so wouldn't be susceptible to the "inflation factor".

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http://bikeblather.blogspot.com/

any updates on the doval?

You are making very strong statements. What do you base them on? Impressions or studies? I'm always wary of absolute statements based on subjective impressions.

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power2max
http://www.power2max.com/northamerica
official power meter of Movistar Team

You are right to be skeptical of absolute statements. And I didn't do a good job of it, but I was trying to make a qualified statement. IF non-round rings improve efficiency or sustained power, then angular adjustment is really essential.

So what do I base that on? Basic physics and geometry. Knowledge of how significantly bike fits vary among individuals. Knowledge of how much frame geometry, especially in the rear triangle, varies among brands. An understanding of how forces are applied on chain-driven mechanisms. The bottom line is that the range of angles between your hip joint and the chainline is huge. And the angle is even affected a lot by many things folks don't consider, like even something as seemingly mundane as your gear choice.

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Interesting/intriguing conversation Tom and others.

A good case has been made about the artifactual inflation of the power numbers reported by crank based PM's. A display of high (or low, take your pick) power numbers during a race/workout has undoubtedly psychological effects. Some might be good, others might be bad. That's a little bit like a "you can do it!" or a "you're in way over your head, buddy!" bouncing inside the head. No doubt. Maybe that's were the value of the Osymmetric/Oval rings resides for some.

Now, another way of looking at the observed inflation would be as the proof that the rings DO change pedal velocity during the 360 rotation. The greater the inflation the greater the change in angular velocities. In my mind then, the question becomes: what are the metabolic/physiological consequences???

If the above is making any sense, perhaps should we look first at pedaling regimes (hill climb, TT, sprinting etc...) were the inflation is the greatest and then try to tease out if the outcome (ie, achieved speed/duration ) is favorable, no?

Well, the point that angular adjustment is really essential is something I am not fully on board with. You seem to be assuming that differences in the angle of the oval are really important. When I compare my road vs TT bike position I am rotated forward around the bottom bracket, but my hip angle seems to stay roughly the same. Neither Qs nor Osymetrics have felt much different between my road and TT bike, despite the different positions. It would be fairest to do a systematic comparison between the different angle options on the Rotors before making a strong recommendation. So before saying that Q-Rings are a "killer app" because of the angular adjustment, I think one would really need to get some info to check it.

As context (and so this is not just about the angle question): I have been using Round rings, Q rings, and Osymetrics in the last two years. At the moment I have Osymetrics on my TT bike and Q rings on my road bike. I have personally not found any differences between round and ovalized rings in absolute power on, say, 20min or 5min tests with my PM, nor on HR to power relationships. However, I have noticed that the muscle groups seem to get used differently and I like the feel of ovalized rings. To me osymetric feel nicer because they are more ovalized, but I don't like the shifting quality. Also like ovalized rings a lot for out of saddle climbing - seems to work really well.

Cheers
Jever

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power2max
http://www.power2max.com/northamerica
official power meter of Movistar Team

Sure, I follow you, but I'm not certain that it's important. More that I'm saying that if a non-circular chainring is important, then it logically follows that angular adjustment is important. It's kind of an 'if a=b and b=c, then a=c' type of argument. You kind of have to think about why the chainring shape is important in the first place. Why does the differing radius make a difference? Because it changes the mechanical advantage that the rider has on the chain. And that increased (and decreased) mechanical advantage depends 100% on where the pushing is coming from (i.e., where the rider's legs are located) and the location of the item being pulled (i.e., the chain). The effectiveness (or lack thereof) of non-round chainrings depends wholly on the angular relationship between the two.

Greg @ dsw

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The angle of the chain doesn't make a difference, as far as I can tell, other than that it changes slightly where the chain contacts the chain ring, and therefore where on the ovalization it is. However, by eyeballing it on my bike it looks like the difference between the biggest and smallest sprocket makes a small difference in terms of contact point.

Secondly the angle at which the oval sits: adjusting it is only important if it was "in the wrong orientation" for what you are doing. If it's in the right place then there is no need to change it. Let's assume the most frequent orientation (position 3 on a Q ring) is "correct" for most road cyclists. You would only want to change that if your pedaling mechanics fundamentally change. The pedaling mechanics would only change if the relative position of your joints relative would change. However, if you just rotate your pedaling motion around the BB, nothing really changes.

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power2max
http://www.power2max.com/northamerica
official power meter of Movistar Team

...and if it isn't important? ;-)

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http://bikeblather.blogspot.com/

Well, then we're just, uh, pondering our belly buttons ...

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I've been running the Doval in its default configuration for over a month now. Still shifts very well, couldn't for the life of me tell you whether or not there was an actual improvment in power, although my average speed has gone up since then I've also started actually training. Rode them on rollers for the first time a couple days ago and was surprise that it was if anything smoother than normal.

Still need to try the "optimal" position but I've been hesitant because not sure how it will affect shifting (ramps and pin placement). I'd be interested to see what Rob finds with his power meter.

EDIT: I've decided to go ahead and bit the bullet I'll switch it to optimal position tonight. I'll let you know if I "feel" anything different.

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Jordan Oroshiba --- Roadie invading Triathlete space for knowledge access

Ok Doval rings set up as close to "Optimal" as I think they will get. About 50 degrees to the minor axis and 110 to the major. (I'm assuming i failed to some extent with these angles so just rounded to the nearest 10). I'll report back if anything feels either terrible or fantastic on this next ride

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Jordan Oroshiba --- Roadie invading Triathlete space for knowledge access

Alright rode them in the "optimal" position this AM, 2 HR tempo ride on my normal 2 hr tempo ride route. I can't say if they were really any better or worse though. It was rainy I was overdressed and it was windy. Anywho: I did notice that my glutes got a little more action and my quads and hamstrings a little less. I'm not sure whether or not this was good but I've been having some knee issues as of late and didn't have those today so it at least seemed to remove some force from those.

This configuration also took a lot longer to "adjust" to which once again I'm not sure if that is good or bad. They do most certainly feel different and when standing they feel like shit (as I largely expected seeing as the dead spot kinda moves a bit and my peak power tends to occur closer to where the easy section of this config is. I'll do at least 2 more weeks of riding on this and then I'm thinking I might switch them to where the major axis is precisely perpendicular to the crank arm.

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Jordan Oroshiba --- Roadie invading Triathlete space for knowledge access

Alright, 2 weeks on them don't like this "optimal" positioning. It feels like it hit the easy spot when I still have power to give and force starts increasing before I have power to give. Also feels like shit out of the saddle. I'm going to try halfway between the stock position and the "optimal" position. If that doesn't work out I'll go back to the stock because I liked that just fine and had multiple of my fastest times on it. I think halfway between will be close to perfect seated not sure about standing.

No real hard science here, but I noticed group rides were a tad harder with this current position and I do a regular route that is about 2 Hrs of tempo, haven't been able to hit it as fast as I did in the stock position. Nothing concrete just what I feel, but if I feel slow I am slow!

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Jordan Oroshiba --- Roadie invading Triathlete space for knowledge access